Adding new columns and simple calculations?

I am trying to add new columns to a worksheet to do a simple difference calculation but am having issues.  Let's say I have 100 rows of data and 4 columns across the top.  The rows are the investment name, the columns are the fund name, and the sum data are % returns.  I am trying to add new columns that show the difference between each fund.  Any ideas?  It is difficult to do this with the raw data before pulling into Tableau.

For instance:

Thank you!

Investment Name     Fund A     Fund B     Fund C     Fund D                    Difference between Fund A and Fund B...etc

ABC Corp                    2%          1%          3.5%          .57%

CBA Corp                     1%          1%          3.5%          .27%

BBB Corp                      2%          1%          4.5%          .37%

DCA Corp                      3%          1%          2.5%          .57%